st: Possible to use stsum with variables that are tvc?

["Wagner, Joseph" <WagnerJ@edc.pitt.edu>]

I used the -tvc- option in an -stcox- command.  Is it possible to use
-stsum- to obtain incidence rates for a variable if it is a time varying
covariate(tvc)?  

Suppose I want the rate of x and I have xdate which is the date when x
begins and represents some portion of a subjects survival time.  If I use:

. stcox tvc(xdate) 

can I obtain the incidence rate from: 	

. stsum x

Or do I need to -stsplit- my data first?
*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/